1. Field of the Invention
This invention relates generally to rollers, and more particularly, to rollers used in crushers.
Crushers are used throughout industry to reduce materials such as coal, rock, salt, granite, etc. from a large size to a smaller size. Crushers designed for this purpose frequently include a pair of crushing rollers between which the material to be crushed is passed to accomplish the desired size reduction. The crushing rollers generally consist of an outer metal shell mounted on an inner hub. The outer shell will wear at different rates, depending on the type of metal and the material being crushed. As the outer shell wears it must be replaced, sometimes as often as once a month.
Some crushing roll shells are currently shrink-fitted onto roll hubs by heating the shell until it expands, sliding it onto the hub and letting it cool, so that the shell shrinks tightly onto the hub. A problem with this method of mounting roll shells is that the shell may crack when it cools, especially if the shell is made from a hard, high carbon steel. High carbon steels are preferable for crusher roll shells because of the relatively long wear life. In addition to cracking, another problem with the shrink-fitting is that the application of heat to the shell may cause so much stress that the shell loses its uniformity and roundness. In most crushing applications, uniform roundness of the crushing rolls is essential in order to obtain a uniform crushed product.
A second method for attaching crushing roll shells to roll hubs utilizes a tapered wedge and a tapered roll shell. The tapered wedge is pulled longitudinally toward the center of the roller, causing inward radial forces against the roll hub and outward radial forces against the tapered roll shell. The radial forces hold the shell in place, but the tapered surfaces make alignment in both the radial and axial directions difficult. Parallel alignment between crushing rolls is also a critical factor in producing a uniform product. A problem which is common to both mounting methods is the extended time required to replace roll shells.
2. Description of Related Prior Art
Several other crushing roller assemblies are disclosed in the art. Thus, U.S. Pat. No. 1,670,381 discloses a crusher roll which utilizes a plurality of wedges 23 adapted to be arranged in one of a plurality of recesses in a hub 10 to join a crusher roll 19 thereto. When the bolts 26 are tightened, they cause a gripping action between the roll 19 and the hub 10.
U.S. Pat. No. 1,885,241 is directed to a crushing roll having a hub portion 8 which lockably supports an outer roll shell 1 for rotation about a shaft 7. The shell has a flange or shoulder 5 in its inner bore which engages a finger 4 on the core member 3. Bolts 14 and 16 are tightened to cause the core 3 to grip the flange 5 tightly and hold the outer roll shell 1 in place.
U.S. Pat. No. 1,674,635 utilizes a segmented expansion mandrel which expands to grip an outer roll shell 25 when cone-shaped elements 30 and 31 are forced into contact with the inner peripheral surface 10 of the mandrel.
Other roll shell mounting assemblies are disclosed in U.S. Pat. Nos. 1,681,868, 3,231,205, 3,761,008 and 4,547,940. However, none of these assemblies adequately addresses the problems discussed above to satisfy today's crushing application needs.
It is an object of this invention to provide a crusher which supplies uniform crushed product and which has extended roll shell wear life. It is a further object to provide a crusher which promotes quick removal and installation of crushing rollers and crushing roll shells.